2.2.3 Cardiac Arrhythmias
Author: Rob Birkinshaw
Background :
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Dysrhythmias are common in the A&E department. Some patients tolerate them well
and others become acutely unwell due to a poor cardiac output.
It is important to differentiate those that need emergent treatment from those in whom
treatment can be delayed until expert advice is sought.
Call for senior help early , particularly if your patient is hypotensive or has chest pain.
Key Points
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Always assess the patient first. Treat the patient and NOT the monitor.
A patient who is talking is usually tolerating their rhythm.
Perform simple manoeuvres first (give oxygen, get an IV line and perform vagal
interventions if you suspect SVT)
Analyse the ECG methodically.
Get a SENIOR early if your patient is compromised. Do not try to treat it yourself.
Bradycardia
Note: Sinus bradycardia may be physiological in hypothermia or in very fit athletes
1.Heart block
Management depends on the underlying cause.
a)Acute myocardial infarction
Inferiors:- heart block rarely needs to be treated with an inferior AMI. Complete heart block
may be symptomatic and should initially be treated with Atropine and then by transcutaneous
pacing.
Anterior:- temporary pacing is indicated for complete heart block with anterior AMI as this is
associated with ventricular standstill. Again initial management should be with Atropine and /
or temporary pacing but always transfer the patient with the external pacer available.
b)Chronic conduction diseases
Complete heart block and high grade second degree block usually require permanent pacing.
Atropine and transcutaneous pacing can be used as a temporising manoeuvre
Syncopal patients should be treated as soon as possible which in A & E means
transcutaneous pacing.
Bradycardia treatment algorithm link is below:
http://www.resus.org.uk/pages/bradpost.pdf
Broad complex tachycardia:
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This may be due to Ventricular Tachycardia or a Supraventricular Tachycardia with
aberrant conduction (which is quite rare).
VT is characterised by AV dissociation, concordance, capture and fusions beats on the
12 lead ECG.
It is a malignant rhythm usually occurring in patients with coexisting ischaemic heart
disease and there is usually systemic upset secondary to a poor cardiac output.
SVT can be tolerated much better unless the rate is such that myocardial perfusion is
impaired.
Adenosine can be used to distinguish SVT with aberrant conduction from VT if the
patient is stable in many cases.
Always treat the patient not the monitor; if in doubt it’s safer to treat as VT.
Key points
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Get senior help early
Use the ALS guidelines for the management of Broad Complex Tachycardias
Patients with signs of cardiovascular compromise require cardioversion
Check Potassium on the blood gas analyser
Supraventricular Arrhythmias
Supraventricular tachycardias
a. Sinus tachycardia is usually not of abrupt in onset and has a rate of <150, always check
for underlying problem, eg hypoxia, pyrexia etc. Treatment is that of the underlying cause.
b. Paroxysmal atrial tachycardia (SVT) is usually abrupt in onset and rate >150. These
patients may have chest pain and be hypotensive if the rate impairs myocardial perfusion. The
rate may be slowed by vagal manoeuvres eg valsalva against a closed glottis or CSM, always
check for a bruit before trying this.
If the patient is compromised then cardiovert with a DC shock starting at 70 -100J.
The best drug to use for chemical cardioversion is adenosine, start with 6mg iv, wait 2 min then
repeat with 12mg, followed by 12 mg. Don't forget to warn the patient that they may
experience a heavy feeling in the arms and chest pain. If adenosine doesn't work then it
probably isn't a SVT!
c. Atrial flutter The atrium always flutters at 300 bpm, the ventricles can't respond to this and
there is always an element of block, so suspect it in rates that are approx 150 bpm(2:1 block).
Again if the patient is compromised then DC cardiovert.
d. Atrial fibrillation. This is very common affecting >10% in the over 70s. It may be a
response to an underlying illness such as pneumonia, sepsis, neoplasm or ischaemic heart
disease. It is important to ascertain how long the rhythm has been established for as this
influences treatment. The decision is whether the patient requires rate control with digoxin or
cardioversion chemically with amiodarone. At present this depends on individual clinical
judgement. Guidelines are being developed to help in this process. As usual if the patient is
hypotensive and unwell they should be considered for cardioversion.
Acute cardioversion whether chemical or electrical carries a risk
phenomenon particularly if AF has been established for at least 48 hrs.
of embolic
How to digitalise someone....0.5 mg of digoxin in 100 ml of normal saline over 30 mins, this can
be repeated every 6 hrs to a total dose of 1.5-2.0 mg. Try and get a potassium before
digitalisation, a low K potentates digoxin induced arrhythmias.
Key points
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Correct biochemical abnormality
If there is serious cardiovascular compromise then cardiovert
Use the ALS guidelines for the management of Narrow Complex tachycardias
Tachycardia treatment algorithm link is below:
http://www.resus.org.uk/pages/tachpost.pdf